Creating Emotion in Games: The Craft and Art of Emotioneering

When characters go through emotional situations but don't react with appropriate emotional responses (or react with no emotional responses at all), it causes the game to have a cartoony feeling. That's okay if that's the effect you want, but most of the time I've seen cartoony reactions by NPCs in games, it's a result of poor writing or design.

Once you decide on the emotional response you want, then you've got to find an artful way to communicate it.